Assault weapons have been in regular military use since at least the Viet Nam war era. Since their first introduction, military specifications have required that a dust gate be in place over the ejection port on all such weapons. An ejection port is an opening within the upper receiver of an assault weapon that allows spent casings to exit after firing. A dust gate is typically located over the ejection port, when the weapon is not being fired, to help prevent contaminants such as sand, dirt, or other debris from entering the mechanism. While most assault weapons have some type of cover to protect internal components from contaminants, the component most often referred to as a “dust gate” is utilized on the ejection port of automatic rifles.
When used on a weapon, the dust gate is held in place in the ejection port with a detent to protect the ejection port and internal components from contaminates. When the weapon is fired, an internal bolt slides past the ejection port, disengaging the detent, so that a biasing-spring on the dust gate can force the dust gate down and against the lower receiver. Occasionally, the dust gate will jam preventing the internal bolt from completing its action, thus disabling the weapon. Under most environmental conditions, a dust gate provides only minimal protection. Because of the potential for jamming the bolt, civilian, as well as active-duty military personnel, often prefer to remove the dust gate from their weapons. However, due to military requirements, the dust gate must be retained and reusable.
Removal of a dust gate can be a tedious process that requires at least partial disassembly of the weapon. Current designs utilize a pivot pin that slides through sleeves on the dust gate and fit into two pin ports on the side of the weapon. To remove the dust gate, the pivot pin can be slid towards the barrel and out of the pin ports and sleeve. There is typically a barrel nut that secures the barrel in place on the lower receiver. The dimensions of the barrel nut prevent the pivot pin from sliding completely out of the sleeves and/or pin ports. Thus, the barrel nut and barrel must be removed to completely release the dust gate. The dust gate can then be retained for later re-installment by the same method. Alternatively, the pivot pin and dust gate can be bent until the pivot pin can be disengaged from the pin ports. This technique will render the dust gate unusable.
Despite the fact that dust gates have been used on automatic weapons for over 50 years, there has been little or no improvement in the design of dust gates and particularly in the methods for removing or installing them on a weapon. To date, removal of a dust gate necessitates either significant disassembly of the weapon or effectively destruction of the pivot pin that holds the dust gate onto the weapon.